The contractor shall prepare and deliver, over a three year period, a source of radiolabeled sphingolipids to the intramural laboratories of the NINDS, which are needed to support basic and clinical investigations of Gaucher's disease, Niemann-Pick disease, and Fabry's disease. Specifically, these radiolabeled sphingolipids are required for: 1) monitoring the catalytic activity and enzymes being developed for replacement therapy in patients with the above mentioned disorders; and 2) elucidation of metabolic errors in patients with these diseases.